FIG. 1 is an external elevational view of a typical building structure BS having walls (e.g. BW) extending uprightly between floor (BF) and ceiling (BC), a wall (e.g. BW) including an upright rectangular door opening D provided with a multi-sections vertically acting overhead type door of the prior art. Rectangular door opening D is typically defined by longitudinally horizontally extending bottom-border DB at floor level BF, by longitudinally horizontally extending top-border DT at wall header BH, and by longitudinally separated and vertically extending left-border and right-border (D1, D2). Located on the internal side of wall BW and parallel to vertical borders D1 and D2 are the vertical lengths TV1 and TV2 of trackways T1 and T2. The horizontal lengths TH1 and TH2 of trackways T1 and T2 are customarily hung parallel to ceiling BC. The several longitudinally extending panel-like sections (S1 . . . Sn) of door DD are sequentially pivotably attached (P, R) and also rollably engaged (M, N, R) to the respective trackways (T1, T2).
The longitudinally extending door sections are conventionally numbered in consecutive ascending order commencing at bottom-section S1 and ending at top-section Sn. Thus, in the five sections door DD arbitrarily chosen for depiction in FIG. 1, the sections occur as bottom-section S1, three medial-sections (S2, S3, and S4), and top-section S5. At the two vertical ends of bottom-section S1, and to provide rollable engagement with trackway lengths TV1 and TV2, there are lower roller units M1 and M2 and also upper roller-hinges R1; the horizontal upper-edge of bottom-section S1 is pivotably connected to the horizontal lower-edge of lowermost medial-section S2 with two endward roller-hinges R1 and with inboard hinges P1. At the two vertical ends of top-section S5, and to provide rollable engagement with trackways T1 and T2, there are upper roller units N1 and N2 and also lower roller-hinges R4; the horizontal lower-edge of top-section S5 is pivotably connected to the horizontal upper-edge of uppermost medial-section S(n-1) e.g. S4, with two endward roller-hinges R4 and with inboard hinges P4. For the horizontal upper-edges of medial-sections S2, S3, and S4, there are endward roller-hinges R2, R3, and R4, and the respectively co-elevational inboard hinges P2, P3, and P4.
In the door-closed condition (shown in FIG. 1), all door sections are engaged along trackway vertical lengths TV1 and TV2, and hence, all sections are maintained in vertical position. In the door-open condition (not shown), top-section Sn e.g. S5, and most of the descending order sections therebelow are engaged with trackway horizontal lengths TH1 and TH2. Vertical doorcables C1 and C2 are attached to the two lower end corners M1 and M2 of bottom-section S1, said doorcables C1 and C2 lying within trackway vertical lengths TV1 and TV2 and being wound around drums KD1 and KD2, said drums being carried by horizontal shaft K attached at header BH with bearing plates KB1 and KB2. KJ1 and KJ2 refer to torsion springs for drums KD1 and KD2, and SH refers to a lifthandle for bottom-section S1.
The prior art ladder-method installation technique for multi-sections vertically acting type doors (DD) requires installing into trackway vertical lengths TV1 and TV2 the sections S1-Sn in ascending order, starting with bottom-section S1, then with medial-sections S2 . . . S(n-1), and finally with top-section Sn e.g. S5. With the prior art ladder-method, the workman is required to tediously and repetitively position, climb, descend, and re-position a ladder, and including lugging the heavy door sections S3, S4 . . . Sn up the ladder. Hence, the prior art ladder-method suffers from the disadvantages of tediousness and coincident high labor costs, the danger of falling ladders, and the inability of all but vigorously endowed youthful workmen to perform the door installation task.